A common way of manufacturing patterned textile fabrics such as carpeting is through the use of yarns or fibers of various colors. Melt or solution dyed yarns are easily distinguishable in the fabric manufacturing process, as their built-in colors are visible to a process operator. The process operator, then, can positively determine from the pattern design if the correct yarn is being fed to the proper segment of the process. This method is quite satisfactory, but requires a large inventory of yarn for different styles and combinations of colors. The inventory requirement usually results in a limited amount of colors.
Another means of manufacturing fabrics with patterned effects involves printing the pattern after formation of the fabric. This technique is useful for woven or knitted fabrics. Techniques have been developed for printing of tufted fabrics. This latter technique is slow and requires sophisticated machinery.
It is also known to tuft carpet fabrics with greige yarns having different dye affinities to form patterning effects. The difficulty with the use of such yarns is the similarity in their before-dye appearance--the yarns are sufficiently similar in color to create confusion in separating the yarns for patterning during processing.
The industry has heretofore resolved this problem by overspraying each different type of yarn with a fugitive tint. Overspraying is a means by which a fugitive tint in a solvent is applied to the surface of fibers. With four common dye variants--light, deep, cationic, and regular --three must be tinted in order to distinguish the four from each other during simultaneous processing.
The problems encountered with tinting the ends in this method are that the tints are unstable and may migrate during processing to other fibers. Further, the tint may interfere with dyeing if the migration pools the tint in any one locale. Further, deep dye polymers are quite receptive to dyes and often the overspray may become permanently affixed in processing.